This invention relates generally to passive, alpha-track radon monitors, and more specifically to an alpha-track radon monitor in which the configuration of the alpha-track registration material is in the form of a flexible strip to facilitate automatic processing of the material.
Radon gas is a naturally occurring radioactive noble gas that results from the decay of radium 226. It has long been recognized that exposure to radon gas (and radon gas daughters that occur as a result of radon gas decay) can pose a significant health hazard. Although testing for radon gas has been done for many years, until relatively recently, concern over exposure to radon gas was primarily associated with workers in the uranium mining industry or others whose work brought them in contact with uranium ore. In recent years, it has also been recognized that radon gas can seep out of the ground through building foundations and can accumulate inside the buildings. When radon gas accumulates in a human environment, it is inhaled thereby exposing the lungs to radioactivity. The health hazards of radon gas exposure are associated with the increased likelihood for the development of lung cancer, which may not occur until 10 to 20 years or more after exposure. Consequently, it is now considered that naturally occurring radon gas can pose a significant health hazard to the general population. The United States Environmental Protection Agency (EPA) estimates that as many as 20,000 deaths occur each year as a result of exposure to radon gas. The U.S. Department of Energy supports the study of radon gas measurement and detection through its Office of Remedial Action and Waste Technology.
Because of the present awareness of the health hazards associated with exposure to radon gas, widespread testing programs have been undertaken and further testing programs are planned. This testing includes buildings such as homes, schools and offices. To achieve widespread testing, it is recognized that many measurements must be made. In fact, it is often considered appropriate to make several measurements in a single building at different locations within the building. The testing for radon gas is normally performed by placement of detector devices in the location to be tested. These detectors typically contain an alpha track registration material, a film which is sensitive to the radioactivity associated with radon gas. After placement of the detectors in the building being tested for an established period of time, typically on the order of several weeks to several months, the detectors are removed from the building and conveyed to a laboratory. At the laboratory, the detectors are analyzed with suitable equipment for the detection and measurement of radon gas. From this analysis a determination of the presence and concentration of radon gas in the building being tested can be inferred.
Typically, exposed registration material is developed by etching with NaOH, and then the developed film is counted by optical or spark counting techniques. Optical counting employs an optical system such as a microscope to magnify the developed alpha-track images so that they can be counted either manually or with automatic counting equipment. Spark counting employs the counting of voltage or current pulses generated by discharges through the etched track in the registration material placed between electrodes. Spark counting techniques however, require the use of registration material having no supporting backing. It is necessary that the material be unbacked so that the holes produced go through the film such that the sparks generated can be counted.
Alpha-track registration material is typically planar. Such material as described or used in U.S. Pat. Nos. 4,778,992, 4,920,272, or Re. 33,065, consists of a rectangular piece of cellulose nitrate in which one or both sides of the film can be exposed to a radon containing environment. After exposure to this environment, the film is individually processed and then the alpha-particle tracks from radon are counted using conventional techniques. Current processing and counting techniques result in a time lag from exposure to counting. Additionally, the use of planar film configurations does not always provide a uniform track distribution. The use of optical counting techniques is time consuming and labor intensive. Further, the use of spark counting techniques can possibly result in a build-up of static charges and cause inconsistent readouts.
Accordingly, it is an object of the present invention to provide a radon monitor in which results from exposure of track registration material can be timely processed.
It is another object of the present invention to provide a radon monitor in which the track registration material provides a uniform track distribution to result in greater radon counting accuracy.
A further object of the present invention is to permit the efficient counting of greater numbers of tracks to improve the sensitivity and accuracy of radon measurement.
Another object of the present invention is to provide a radon track registration material which is flexible, configured to provide a greater degree of counting accuracy, and which is capable of being combined with material from a plurality of monitors to facilitate automatic processing.